Abstract

A multicentre, double-blind, placebo-controlled, randomised phase III clinical
trial was conducted in Japanese patients with well-defined IPF to determine
the efficacy and safety of pirfenidone, a novel antifibrotic oral agent, over
52 weeks. Of 275 patients randomised (high-dose, 1,800 mg·day−1; low-dose, 1,200 mg·day−1; or
placebo groups in the ratio 2:1:2), 267 patients were evaluated for the
efficacy of pirfenidone. Prior to unblinding, the primary end-point was revised;
the change in vital capacity (VC) was assessed at week 52. Secondary
end-points included the progression-free survival (PFS) time.

Significant differences were observed in VC decline (primary end-point)
between the placebo group (-0.16 L) and the high-dose group (-0.09 L) (p = 0.0416);
differences between the two groups (p = 0.0280)
were also observed in the PFS (the secondary end-point). Although
photosensitivity, a well-established side-effect of pirfenidone, was the major
adverse event in this study, it was mild in severity in most of the patients.

Pirfenidone was relatively well tolerated in patients with IPF. Treatment
with pirfenidone may decrease the rate of decline in VC and may increase the
PFS time over 52 weeks. Additional studies are needed to confirm these findings.

Pirfenidone (5-methyl-1-phenyl-2-[1H]-pyridone; Shionogi &
Co., Osaka, Japan; MARNAC, Dallas, TX, USA) 7–9 is a promising
agent with therapeutic potential for IPF that has combined anti-inflammatory,
antioxidant and antifibrotic effects in experimental models of pulmonary fibrosis 10–14. Following an open-label phase II pioneer study 7 and an open-label 1-yr study in Japan 9, a double-blind, placebo-controlled clinical
trial of pirfenidone in Japanese patients with IPF demonstrated a lesser decline
of vital capacity (VC) in patients receiving pirfenidone for 9 months 15. The trial was prematurely terminated
by the independent Data and Safety Monitoring Board (DSMB) because
of a higher incidence of acute exacerbations in the placebo group than the
pirfenidone group. These encouraging results, prompted us to undertake a phase
III 1-yr clinical study to examine the therapeutic effects of pirfenidone
on lung functional deterioration and disease progression in patients with
IPF.

MATERIALS AND METHODS

Study subjects

The diagnosis of IPF was in accordance with the American Thoracic Society (ATS)/European
Respiratory Society (ERS) Consensus statement 16 and the fourth version of the clinical diagnostic
criteria guidelines for idiopathic interstitial pneumonia in Japan 17. High-resolution computed tomography (HRCT)
scans of the chest were reviewed by expert chest radiologists prior to randomisation;
two out of six expert radiologists independently evaluated the HRCT images
to agree and determine whether the pattern of usual interstitial pneumonia (UIP)
was present or not in accordance with the predetermined protocol (see
online supplementary material). In cases of disagreement, the interpretation
of the third radiologist influenced the final decision, and the diagnosis
of patients with probable UIP pattern on HRCT was confirmed by the presence
of histopathological UIP pattern in surgical lung biopsy samples.

Eligible patients were adults (20–75 yrs of age)
with IPF diagnosis based on the above criteria and meeting the following arterial
oxygen saturation measured by pulse oximetry (Sp,O2) criteria: 1) oxygen desaturation of ≥5%
difference between resting Sp,O2 and the lowest Sp,O2 during a 6-min steady-state exercise test (6MET);
and 2) the lowest Sp,O2 during the 6MET
of ≥85% while breathing air. The 6MET procedure was in accordance
with previous study protocols (see online supplementary material).
Exclusion criteria were: 1) a decrease in symptoms during the preceding
6 months; 2) use of immunosuppressants and/or oral corticosteroids
at a dose >10 mg·day−1 during the preceding
3 months; 3) clinical features of idiopathic interstitial pneumonia other
than IPF; 4) evidence of known coexisting pulmonary hypertension, asthma,
tuberculosis, bronchiectasis, aspergillosis or severe respiratory infection.

The protocol was approved by the institutional review board at each centre
and written informed consent was obtained from all participants prior to enrolment.
The ongoing efficacy and safety results were reviewed by the independent DSMB.

Study design

This study was a multicentre, double-blind, randomised, placebo-controlled,
phase III clinical trial designed to determine the efficacy and safety of
oral administration of pirfenidone for 1 yr in patients with IPF. Eligible
patients were allocated to three groups: high dose (1,800 mg·day−1), low dose (1,200 mg·day−1) and placebo, in a ratio of 2:1:2, respectively, with a modified
minimisation method, including some random allocation based on biased coin
design to balance baseline Sp,O218, 19.

Treatment regimen

Pirfenidone as 200-mg tablets and matching placebo were provided for oral
use by Shionogi & Co. The dose was increased in a stepwise manner as follows:
one tablet t.i.d. orally administered for the first 2 weeks (high
dose 600 mg·day−1, low dose 600 mg·day−1 and placebo 0 mg·day−1),
then two tablets per dose t.i.d. for the following 2 weeks (high
dose 1,200 mg·day−1, low dose 600 mg·day−1 and placebo 0 mg·day−1)
and three tablets t.i.d. for the remaining 48 weeks (high dose
1,800 mg·day−1, low dose 1,200 mg·day−1 and placebo 0 mg·day−1) (see
online supplementary material). Although concomitant use of corticosteroid ≤10 mg·day−1 (as the prednisone equivalent) was permitted during
the study period, concomitant use of immunosuppressants and other experimental
agents under investigation was not allowed (see online supplementary
material). All participants were forewarned of the potential photosensitivity
skin rash and were advised to use sunscreens during exposure to direct sunlight.

Efficacy end-points

The primary end-point was the change in VC from baseline to week 52. Secondary
end-points were progression-free survival (PFS) time and the change
in the lowest Sp,O2 during the 6MET. The progression
of disease was defined by death and/or ≥10% decline in VC from
baseline. When the VC data could not be obtained due to worsening of respiratory
symptoms, including acute exacerbation, the case was also classified as disease
progression. As in the phase II study conducted in Japan 15, the 6MET procedure had been prespecified in the
protocol (see online supplementary material). Tertiary end-points
were pulmonary function tests (PFTs; arterial oxygen tension, alveolar–arterial
oxygen tension difference at rest, total lung capacity (TLC) and
diffusing capacity of the lung for carbon monoxide (DL,CO)), acute exacerbation 20, serum levels of the markers of interstitial pneumonias (sialylated
carbohydrate antigen KL-6, surfactant protein (SP)-D and SP-A; see
online supplementary material) and subjective/objective symptoms (cough,
presence/absence of sputum and dyspnoea in daily living assessed with
Hugh–Jones classification).

VC was measured every 4 weeks, whereas the lowest Sp,O2 during the 6MET and other PFTs were determined every
12 weeks. Acute exacerbation of IPF was defined according to previous
reports and revised criteria for acute exacerbation of IPF in Japan (see
appendices in online supplementary material) 15, 20.

The change in the lowest Sp,O2 during the
6MET over 52 weeks was the original intended primary end-point for
this study. The decision was made to revise the primary end-point from the
lowest Sp,O2 to VC at week 52 and assess the
change in the lowest Sp,O2 during the 6MET
as a secondary end-point. This was recommended by the independent DSMB, prior
to breaking the code. This decision was based on the evolved knowledge of
assessment with objective measurements in IPF 21–26, as
well as the lack of validation in the 6MET study (unpublished data)
and difficulties in reproducibility of the Sp,O2
measurements during the 6-min walk test (6MWT) 27.

Statistical analysis

The planned sample size was 250 in total: 100, 50 and 100 patients in the
high-dose, low-dose and placebo groups, respectively. The sample sizes of
100 for the high-dose and placebo groups were determined on the basis of simulations
that would provide a statistical power of 0.8 to detect assumed differences
of the mean changes in the lowest Sp,O2 from
baseline to week 52 between the two groups at a significance level in this
study of 0.1 (two-sided) (details in the online supplementary
material). Although the primary end-point was altered from the lowest Sp,O2 to VC after the study was started, the power
calculated on the basis of the change in VC turned out to be the same (maintained
at ∼0.8) and, thus, the planned sample size was not altered. As the
low-dose group was intended to assess benefit–risk profiles of pirfenidone
treatment at a tapered dose, the sample size of the low-dose group was obtained
by halving the sample size of the high-dose and placebo groups. Multiplicity
problems were not taken into account because the main analysis was the comparison
between the high-dose and placebo groups.

Analyses of the change in VC and the lowest Sp,O2
from baseline were performed with ANCOVA using the respective baseline measurements
as covariates. Analyses of the change in other PFTs and the serum levels of
the markers of interstitial pneumonias were performed with the least significant
difference method based on one-way ANOVA. The principle of the last observation
carried forward (LOCF) was adopted to impute missing values if patient
data were available for ≥4 weeks after the baseline. In order to
avoid bias when dealing with missing values, the mixed model approach using
the available repeated measures of changes in VC was performed as a sensitivity
analysis. The cumulative PFS rates were estimated using the Kaplan–Meier
method and compared using the log-rank test. Incidences were compared with
Fisher's exact test.

RESULTS

Patients enrolled

Between July 2004 and August 2005, 325 patients were screened at 73 centres
in Japan, and 275 patients were randomised to one of the three groups: high
dose, low dose and placebo. Of the 275 patients, 267 (108, 55 and 104
patients in the high-dose, low-dose and placebo groups, respectively)
were deemed eligible for the full analysis set. Eight patients were excluded
because no post-baseline data were available (fig. 1⇓). The first patient entered the trial
on July 13, 2004, and the last patient entered on August 30, 2005.

Disposition of patients. 325 patients were screened at 73 centres
in Japan and 275 patients were randomised to one of the three groups: high-dose (1,800 mg·day−1 of pirfenidone), low-dose (1,200 mg·day−1) and placebo groups. Disease progression included a 10%
decline in vital capacity and worsening of respiratory symptoms.

No significant differences were seen in the distribution of the demographic
and baseline characteristics among the three groups, except for smoking history (table 1⇓). A post analysis did not reveal a
significant effect of smoking history on the change of VC. Based on their
PFTs, patients had been assumed to have relatively mild functional impairment.
246 patients (92%) had not received prior treatment for IPF,
including corticosteroids. 86 patients (40, 15 and 31 patients in the
high-dose, low-dose and placebo groups, respectively) discontinued the
study medication for various reasons (table 2⇓). The main reasons were progression of disease
in the placebo group, and the occurrence of adverse events in both pirfenidone
treatment groups. A Kaplan–Meier plot of the time to discontinuation
for the three groups is shown in Figure E1 of the online supplementary material.
The time distributions were compared in pairs among the three groups using
the log-rank test, but no significant differences were seen. 11 patients (4.1%)
died during the study: three, four and four in the high-dose, low-dose and
placebo groups, respectively.

Effects on primary end-points

The adjusted means of the changes in VC based on the ANCOVA were -0.09 L
and -0.16 L in the high-dose and placebo groups, respectively, with
a difference of 0.07 L being significant (p = 0.0416).
In addition, the adjusted mean change in the low-dose group was -0.08 L;
a significant difference was also seen between the low-dose and placebo groups (p = 0.0394) (fig. 2⇓). The crude means (at baseline
and week 52) and the changes, the adjusted means, mean changes from ANCOVA
and the p-values are summarised in table 3⇓.
No significant difference was seen between the high- and low-dose groups.
The serial changes in VC over the 52-week period are illustrated in figure 3⇓.

Effects on secondary and tertiary end-points

The secondary end-points were PFS time and the change in the lowest Sp,O2 during the 6MET. The distribution of PFS
time was compared between the high-dose and placebo groups with the log-rank
test, and a significant difference was found (p = 0.0280;
fig. 4⇓). In addition,
a marginally significant difference was found in the distribution between
the low-dose and placebo groups (p = 0.0655).
No statistically significant difference was detected in the mean changes of
the lowest Sp,O2 among the three groups (table 4⇓). The incidence of acute exacerbation
during the study or within 28 days after the termination of the study
was six (5.6%), three (5.5%) and five (4.8%)
in the high-dose, low-dose and placebo groups, respectively. No significant
differences were seen among the three groups. Although between the low-dose
and the placebo groups the differences of mean changes in TLC and changes
in DL,CO were statistically significant (p = 0.0408
and p = 0.0768, respectively) at week 52, there
were no significant differences in the changes of other PFTs or serum markers
among the three groups (table E1 in the online supplementary material).

Kaplan–Meier plot of progression-free survival time among
idiopathic pulmonary fibrosis patient groups. –––: high
dose; ----: low dose; ·······:
placebo. Symbols on the curve represent the censored points where patients
discontinued the study treatment due to causes other than progression of the
disease. Kaplan–Meier curves were compared with the log-rank test: p = 0.0280
between the high-dose group and placebo group; p = 0.0655
between the low-dose group and placebo group; p = 0.9106
between the high-dose group and low-dose group.

Comparison of changes in the lowest arterial oxygen saturation
measured by pulse oximetry

Compliance and safety

Significant adverse events reported with a frequency of ≥5% during
the study (p<0.05) are listed in table 5⇓. Photosensitivity, anorexia, dizziness and elevated γ-glutamyl-transpeptidase (γ-GTP)
were significantly more common in the high-dose group than in the placebo
group, and photosensitivity, asteatotic eczema, abdominal discomfort and decrease
in white blood cells were significantly more common in the low-dose group
than in the placebo group. In contrast, respiratory tract infection, such
as nasopharyngitis and upper respiratory tract inflammation, was significantly
less common in the high-dose group than the placebo group.

The adverse events leading to discontinuation of the study are listed in
table 2⇑. 20 (18.3%)
patients in the high-dose group and 11 (20%) in the low-dose
group discontinued the study treatment, with no statistical differences compared
to 14 (13.1%) patients in the placebo group. Most of the
adverse events disappeared with a decrease in the dose or temporary withholding
of the medication. Therefore, treatment with pirfenidone was generally well
tolerated in patients with IPF.

Photosensitivity was the major adverse event observed in 51% of
the patients in the high-dose group and 53% in low-dose group. Of the
patients who developed photosensitivity, ∼70% and 80% in
the high-dose and the low-dose groups, respectively, were mild cases and the
remainder were moderate cases. Although there were no significant differences
in the incidence between the high-dose and low-dose groups, the percentage
of mild photosensitivity was higher in the low-dose group. The assessment
of the degree of the severity was subjective, based on the patient’s
symptoms and the site investigator's judgement. Only three patients (∼3%)
discontinued the study due to photosensitivity.

DISCUSSION

During the last decade, several clinical trials for IPF have been conducted
worldwide to determine an effective treatment regimen for IPF, but the results
have been negative and disappointing. Thus, an effective treatment regimen
compared with placebo controls is yet to be determined 5, 6, 21, 28. In this trial, both high- and low-dose pirfenidone groups
improved VC, and the distribution of PFS was better than in the placebo group (fig. 2⇑, table 3⇑,
fig. 4⇑). Recent studies
have confirmed that a fall in VC or forced vital capacity (FVC)
of ≥10% from the baseline over a period of 6–12 months
is the most important predictor of mortality in patients with IPF 22–24, 26. Therefore,
disease progression, defined as time to death and/or ≥10% decline
in absolute changes in measured VC, is acknowledged as an appropriate surrogate
marker for survival 6, 23 that is also appropriate regarding lesser
changes in FVC reported recently 29.
Considering that >90% of patients had not received any treatment
prior to randomisation, our findings provide first evidence that a treatment
intervention with a drug improves PFS time in patients with IPF.

No significant differences were found with respect to the changes in the
lowest Sp,O2 among the groups in our study (table 4⇑). While the exact reasons for these
apparent negative observations are unknown, the following facts may explain
our observations relating to the discrepancy in findings between the previous
study 15 and the present one:
1) the 6MET performed in this and the previous study is not a validated
test, and 2) the final change in the lowest Sp,O2 could not be accurately evaluated because ∼20% of
the patients could not complete the 6MET during follow-up as their lowest Sp,O2 had reached 82% (data not shown).
Reproducibility of the exercise studies with the 6MWT and modified versions
of the 6MWT/6MET are confounding factors that need to be clarified for
future studies before embarking on exercise studies such as the 6MET/6MWT 6, 28.

The previous phase II trial in Japan was terminated early because of the
incidence of acute exacerbations of IPF 15. However, in the present trial, no differences were found in
the frequency of acute exacerbation among the three groups. While the incidence
of acute exacerbation in the placebo group was 14.3% over 9 months
in the previous study, this was observed in only 4.8% over 52 weeks
in the current study, and, thus, the previous observation was not confirmed
in the present study. The reasons for this discrepancy are unclear. In the
present study, acute exacerbation occurred in only 5% of the patients
with relatively mild pulmonary function impairment during 1 yr. The
true incidence and prevalence of the acute exacerbation of IPF is unknown;
the frequencies of acute exacerbation have been reported to differ among studies,
which are largely retrospective 30.
Nevertheless, our observations regarding acute exacerbation warrant further
studies to carefully assess the problem in a well-defined, larger study with
longer follow-up data.

The post hoc analysis based on respiratory function categories
was carried out in this study to compare the results from our previous phase
II study 15. The improvement
ratings of each respiratory function were defined by ATS criteria. There was
no significant difference between the high-dose group and the placebo group (see
online supplementary material, Fig. E2-1). The reasons for the differences
between the two studies are unknown. However, the difference between the high-dose
group and the placebo group was significant (p = 0.0053)
when the categorised analysis of the changes in VC was based on the rating
of a lesser magnitude (see online supplementary material, Fig. E2-2) 29.

The adverse event that occurred significantly more often among patients
in both the high- and low-dose pirfenidone groups was photosensitivity, a
well-known side-effect associated with pirfenidone that has been documented
in previous studies 7, 15. Anorexia and elevated γ-GTP were
significantly more common in the high-dose group than in the placebo group,
similar to results observed in our phase II study 15. Although the overall incidence of adverse events in the pirfenidone
treatment groups was relatively high, no significant differences were detected
in the frequency of the patients who discontinued the study between the pirfenidone
treatment groups and the placebo group. This may be in part that the patients
were well informed regarding the side-effect of rashes. Despite the manifestation
of the anticipated skin rash, pirfenidone was generally well tolerated in
IPF patients.

Potential limitations of this study include changing the primary end-point
during the study. Despite the evolved knowledge that the change in VC at 12 months
correlated well with survival 22–24, 26, we had initially chosen the lowest Sp,O2 during the 6MET as the primary end-point for this study as we
had been encouraged by the novel observations in our previous study 15. Change in VC was initially intended
to be a secondary end-point. Acknowledging that the 6MET employed in our phase
II study needed to be validated, a validation study was planned to evaluate
the lowest Sp,O2 during the 6MET prior to the
initiation of the phase III study (research supported by health and labour
sciences research grants). VC and PFS were selected as key secondary
end-points to support the primary end-point, and the power of test for VC
and PFS was based on the sample size calculated from the lowest Sp,O2 in the first version of the protocol itself. However,
significant difficulties were confronted during the validation study for the
6MET and several patients dropped out of the phase III study. Because of the
concerns of assessing the efficacy of pirfenidone based on the lowest Sp,O2 measured every 12 weeks compared with
the VC measured every 4 weeks and of the potential for unexpectedly
large fluctuations between each point in the lowest Sp,O2 along with the problems of reliability/reproducibility of
the Sp,O2 measurement during exertion such
as walking 27 and acknowledging
that the change in VC or FVC was increasingly being used as the primary end-point
in other clinical studies 5, 21, the primary end-point was changed from
the lowest Sp,O2 during the 6MET to VC during
the study period. While this change in the primary end-point may be considered
as a major limitation for this study, it should be noted that the decision
to change the end-point was prior to code-breaking according to the recommendation
of the independent DSMB, and the sample size was unaffected.

We acknowledge the limitations of dealing with missing values. It is generally
known that results of analyses may have potential bias when missing values
are imputed by an arbitrary method, and that there is no perfect imputation
method which performs best under all circumstances. In this study, we adopted
LOCF, since LOCF had been adopted in the previous study. We were under the
impression that LOCF would not tip the balance in favour of either of the
treatment groups, if there were no substantial differences in the rate of
drop-outs. The mixed model approach using repeated measures of changes in
VC without LOCF imputation as a sensitivity analysis also showed significant
or marginally significant treatment effects and supported the LOCF analysis.
Figure 3⇑ shows the transitional
plot of the changes in VC over 52 weeks. Both the “LOCF imputed means”
and “crude means” of the changes within 16 weeks suggested
a favourable effect of pirfenidone and were not affected by drop-outs.

Other potential limitations of our study include the following. 1)
A selection bias, as patients enrolled in this study needed to be able to
perform the 6MET at baseline in accordance with the protocol; the results
in this selected group of patients with mild functional impairment may not
therefore be applicable to all patients with IPF with varying degrees of pulmonary
symptoms and functional impairment. 2) The lack of a central pathology
review. While we acknowledge these limitations, it must be noted that the
patient population enrolled in this study included all consecutive, eligible
and consenting patients from the general patient population with IPF with
mild functional impairment.

In conclusion, the results of the phase III clinical trial demonstrate
that pirfenidone, a novel antifibrotic agent, preserves VC and improves PFS
better than placebo in Japanese patients with IPF with mild functional impairment
without serious adverse events. Future studies may confirm our findings further.

Support statement

This work was supported by a grant-in-aid for and by members of interstitial
lung diseases from the Japanese Ministry of Health, Labor and Welfare, and
also by members of the Japanese Respiratory Society's committee for diffuse
lung diseases.

Clinical trial

This clinical trial was registered with the Japan Pharmaceutical Information
Center (JAPIC) on September 13, 2005 (registration number:
JAPICCTCI-050121).

Taniguchi H, Kondoh Y. Revised criteria for acute exacerbation
of idiopathic pulmonary fibrosis. The Annual Report by Study Group of Ministry
of Health and Welfare for Diffuse Lung Disease. Diffiuse Lung Diseases Research
Group from the Ministry of Health, Labor and Welfare of Japanese Government,
2004; pp. 114–119